Mainstream is his second company, which he launched in 2008 - the first being Airtricity. Since then he has led the company into new and developing markets, notably Chile and, most recently, South Africa where this year it started development of over 350MW. Private equity firm Marubeni bought 25% of the company last year. Today, Mainstream's footprint reaches far and wide and its healthy pipeline promises 14GW, almost equally split between onshore and offshore capacity. But, having just 234MW in operation or construction is reflected in O'Connor's fall from position 12 in last year's rankings as other developers expand more rapidly.